docs/user_guide/timestamped_data/data_synchronisation.md


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Data synchronisation
====================

Recorded data needs to be synchronized to link them before further processings. 

The [TimeStampedBuffer](/argaze/#argaze.DataStructures.TimeStampedBuffer) class provides various methods to help in such task.

## Pop last before

![Pop last before](../../img/pop_last_before.png)

The code below shows how to use [pop_last_before](/argaze/#argaze.DataStructures.TimeStampedBuffer.pop_last_before) method in order to synchronise two timestamped data buffers with different timestamps:

``` python
from argaze import DataStructures

# Assuming A_data_record and B_data_record are [TimeStampedBuffer](/argaze/#argaze.DataStructures.TimeStampedBuffer) instances with different timestamps

for A_ts, A_data in A_data_record.items():

       try:
              
              # Get nearest B data before current A data and remove all B data before (including the returned one)
              B_ts, B_data = B_data_record.pop_last_before(A_ts)

       # No data stored before A_ts timestamp
       except KeyError:

              pass

```

## Pop last until

![Pop last until](../../img/pop_last_until.png)

The code below shows how to use [pop_last_until](/argaze/#argaze.DataStructures.TimeStampedBuffer.pop_last_until) method in order to synchronise two timestamped data buffers with different timestamps:

``` python
from argaze import DataStructures

# Assuming A_data_record and B_data_record are [TimeStampedBuffer](/argaze/#argaze.DataStructures.TimeStampedBuffer) instances with different timestamps

for A_ts, A_data in A_data_record.items():

       try:

              # Get nearest B data after current A data and remove all B data before
              B_ts, B_data = B_data_record.pop_last_until(A_ts)

       # No data stored until A_ts timestamp
       except KeyError:

              pass

```

## Get last before

![Get last before](../../img/get_last_before.png)

The code below shows how to use [get_last_before](/argaze/#argaze.DataStructures.TimeStampedBuffer.get_last_before) method in order to synchronise two timestamped data buffers with different timestamps:

``` python
from argaze import DataStructures

# Assuming A_data_record and B_data_record are [TimeStampedBuffer](/argaze/#argaze.DataStructures.TimeStampedBuffer) instances with different timestamps

for A_ts, A_data in A_data_record.items():

       try:
              
              # Get nearest B data before current A data
              B_ts, B_data = B_data_record.get_last_before(A_ts)

       # No data stored before A_ts timestamp
       except KeyError:

              pass

```

## Get last until

![Get last until](../../img/get_last_until.png)

The code below shows how to use [get_last_until](/argaze/#argaze.DataStructures.TimeStampedBuffer.get_last_until) method in order to synchronise two timestamped data buffers with different timestamps:

``` python
from argaze import DataStructures

# Assuming A_data_record and B_data_record are TimeStampedBuffer instances with different timestamps

for A_ts, A_data in A_data_record.items():

       try:
              
              # Get nearest B data after current A data
              B_ts, B_data = B_data_record.get_last_until(A_ts)

       # No data stored until A_ts timestamp
       except KeyError:

              pass

```